1. Field of Invention
The present invention relates to pneumatically actuated water control gates and the installation and maintenance methods therefore.
2. Description of Related Art
Pneumatically operated water control gates are well known. Prior art includes U.S. Pat. No. 4,780,024 October 1998 to Obermeyer et. al., U.S. Pat. No. 5,092,707 March 1992 to Obermeyer, U.S. Pat. No. 5,538,360 July 1996 to Obermeyer, U.S. Pat. No. 5,642,963 July 1997 to Obermeyer, U.S. Pat. No. 5,709,502 January 1998 to Obermeyer, U.S. Pat. No. 5,713,699 February 1998 to Obermeyer et. al., European Patent Application Number 02746956 July 2002 Obermeyer, Henry K., International Application Number is PCT/US02/21766.
Construction of underwater structures which include pre-cast concrete portions are also well known. Such construction has, in the past, been hindered by the strength limitations of newly pre-cast concrete elements and by the difficulty involved with turning them over and placing them without damage and without waiting for substantially full cure of the concrete. In the interest of economy, pre-cast concrete slab-like shapes need to be large. In order to limit weight to within the capacity of available lifting equipment such slab-like shapes need to be relatively thin. Construction methods of the prior art have used concrete forms to establish the shape and dimensions of the slab-like structures and then used elaborate lifting beams to carefully distribute loads during lifting, transport and placement.
Conventional water control gate systems across wide rivers or other bodies of water usually incorporate a plurality of intermediate piers that may be used to locate and support movable dewatering bulkheads and gate operating equipment. Such piers are expensive, create excessive and concentrated foundation loads, and may be undesirably susceptible to earthquake damage. Such piers also pose a serious hazard to navigation, especially under high flow conditions when the gates between piers are open.
Other water control gate systems of prior art such as described in U.S. Pat. No. 5,178,490 utilize hydraulic cylinders mounted beneath a plurality of water control gates. Such systems generally require expensive access tunnels and require labor and equipment intensive methods for dewatering for maintenance and repair. Furthermore, hydraulic cylinders, when used in a submerged river environment, are prone to corrosion, abrasion damage, impact damage, and oil leakage.